Konstru has a new element type called Lines
With Lines you can export simple Model Lines from Revit and bring them into ETABS or SAP as frames with "None" sections applied. And Frames with no section will translate into Model lines in Revit the way back as well. You can use the new Line components in Grasshopper to create or read lines using GH. This way you can define members which don't have a defined section yet.